There is about one motor vehicle for every eleven persons on earth. Some 400 million cars and trucks are operated throughout the world. The bulk of these vehicles operate in North America and Western Europe. Over 40% of the world's vehicles, about 176 million cars and trucks are operated in the United States. Homogeneous-charge engines power the vast majority of motor vehicles. In these engines it is attempted to develop a homogeneous mixture of air and fuel vapor by fuel injection or carburation into an intake manifold for delivery to the engine's combustion chambers. Homogeneous-charge engines present numerous problems including:
1. Unburned hydrocarbons and carbon monoxide emissions are unacceptable from homogeneous-charge engines. These emissions are caused by quenching of homogeneous-charge combustion processes near combustion-chamber walls. All major cities are polluted by carbon monoxide and unburned hydrocarbons from homogeneous-charge engines.
2. Another cause of unburned hydrocarbons and carbon monoxide from homogeneous-charge engines is operation at insufficient air to fuel ratios to complete combustion processes at the relatively high piston speeds of modern cars. It is a widespread practice to operate the engine at air-fuel ratios for best power production in spite of the fact that operation at excess-air conditions would produce less unburned hydrocarbons and carbon-monoxide emissions.
3. Oxides of nitrogen emissions are unacceptable from homogeneous- charge engines. Increasing the air to fuel ratio as in homogeneous-charge "lean burn" operations increases production of oxides of nitrogen.
4. Several catalytic processes and an auxiliary air supply are needed to clean-up the exhaust streams of homogeneous-charge engines. Modern cars operating at air-fuel ratios optimized for driveability and minimal oxides of nitrogen require addition of air to the exhaust stream for purposes of catalytic combustion of unburned hydrocarbons and carbon monoxide.
5. Unacceptable energy waste occurs as a great percentage of the fuel present in a homogeneous charge burns near combustion chamber surfaces. Heat is transferred to metallic components including the head, valves, cylinder liner, piston and rings without doing useful work.
6. Homogeneous-charge engines must be limited in compression ratio to values that prevent detonating ignition and piston damage. Positive ignition is achieved by spark plugs.
Technology which has been accepted for improving the thermal efficiency of internal combustion engines includes the venerable Diesel engine apparatus and method of direct injection of fuel into the combustion chamber. This technology is characterized as compressing air to produce sufficiently high temperatures to evaporate, chemically crack, and ignite fuel that is sprayed into the compressed air. Such technology requires fuels with specific characteristics that facilitate "compression ignition". Fuels suitable for compression ignition engines have high "cetane" ratings. Direct-injection compression engines often obtain about two times higher miles per fuel-BTU ratings than homogeneous-charge engines in practical duty cycles because of stratified charge advantages of more complete combustion and reduced heat losses from combustion products to engine components.
A substantial problem with the compression ignition engine is the engine weight penalty that stems from requiring about two times more displacement than spark ignited engines of equal power ratings. In operation, this translates to a much larger crankshaft, a larger flywheel, a larger engine block, larger bearings, larger starter motors, heavier-duty batteries, larger tires, heavier springs, bigger shock absorbers, and a much larger requirement for critical alloying resources such as molybdenum, chromium, vanadium, copper, nickel, tin, lead, antimony, and content of manufacturing energy to mine, refine, cast, heat treat and machine than spark-ignited engines. Other difficult if not unacceptable problems include:
1. Diesel engines are notorious for belching clouds of black smoke during stop and go duty cycles. Bus and truck emissions of nauseous, burned-oil smelling, black smoke in city traffic are unacceptable in view of recent efforts by virtually every city of the world to reduce atmospheric pollution from motor vehicles.
2. Diesel engines are extremely difficult to convert to oxygenated fuels (CH.sub.3 OH, C.sub.2 H.sub.5 OH, etc.) or other clean burning fuels (such as natural gas and hydrogen) because such preferred fuels have high octane ratings and low cetane ratings. Diesel engines require a high cetane rated pilot fuel (Diesel fuel) to torch-ignite clean burning fuels that are "fumigated" into the combustion chamber along with air supplies during intake cycle operations.
3. Fumigation of fuels into the combustion chamber along with air during the intake cycle derates the engine because the fumigated fuel uses part of the breathing capacity and reduces effective volumetric efficiency of the converted engine.
4. Compression ignition engines are hard to start in cold weather. Cold air and cold engine components rob the heat of compression before temperatures are reached that will cause fuel to be evaporated, chemically cracked, and ignited. Expensive subsystems such as spark-ignited starter engines, glow plugs, electric block heaters, and starter fluid dispensers are used in attempts to overcome the difficulties of starting compression-ignition engines in cold weather. Frequently owners of vehicles with compression-ignition engines opt to keep the engine running day and night in the cold season at whatever fuel expense is incurred rather undergo the ordeal of trying to start a Diesel engine in cold weather.
5. Compression-ignition engines operate best in a narrow range of torque-speed conditions. This is because of the characteristic called Diesel-ignition delay and the requirement to tailor the amount of fuel introduced and timing of fuel introduction with respect to the piston speed in order to avoid needless if not damaging pressure rise during the compression cycle and to avoid energy waste and smoke from late burning during the power cycle.
6. Compression-ignition engines require the use of high cetane fuels with carbon to hydrogen mass ratios of about 7. Such fuels and their products of combustion have large radiant energy losses to combustion chamber walls during burning processes. It would greatly improve thermal efficiency to use cleaner burning fuels that have lower carbon to hydrogen mass ratios and much lower radiant energy losses but such fuels cannot be compression ignited in conventional engines.
7. Friction losses are larger in longer stroked, higher compression, and larger bearing area Diesel engines than in spark-ignited engines of the same power rating. In addition to robbing potential power this requires more investment in expensive alloys, case hardening, heat treatment and wear reducing design considerations than required for spark-ignition engines.
Technology for combining the advantages of spark ignition and stratified charge burning have been demonstrated. U.S. Pat. Nos. 3,830,204; 3,094,974 and 3,316,650 and the references cited therein disclose methods and apparatus for introducing fuel directly into the combustion chamber to form a stratified charge mixture of spark-ignitable fuel and ignition of such stratified charges by a spark source. Other published references include "Fuel Injection and Positive Ignition--A Basis For Improved Efficiency and Economy, Burning a Wide Range of Fuels in Diesel Engines"; by Davis, C. W.; Barber, E. M.; and Mitchel, Edward, SAE Progress in Technology Review Vol. II;. Society of Automotive Engineers, New York, NY 10017, 1967, pp. 343-357; "Deutz Converts Operation By Adding High-Tension Ignition System" by Finsterwalder, Gerhard, Automotive Engineering, December 971, pp. 28-32. Institute of Mechanical Engineers Conference Proceedings, Fuel Economy and Emissions of Lean Burn Engines, 1 Mech E Conference Publications,; Mechanical Engineering Publications, Ltd., London, 1979; Institute of Mechanical Engineers Conference Proceedings, Stratified Charge Engines, 1 Mechanical Engineering Conference Publications 1976,; Mechanical Engineering Publications, Ltd., London, 1977; "An Update of the Direct Injected Stratified Charge Rotary Combustion Engine Developments at Curtiss-Wright" by Jones, Charles; Lamping, H. D.; Myers, D. M.; and Lloyd, R. W., SAE International Automotive Engineering Congress and Exposition, Paper No. 770044, February 1977; Society of Automotive Engineers, New York, NY, 1977; "An Update of Applicable Automotive Engine Rotary Stratified Charge Developments" by Jones, Charles, SAE Technical Paper Series No. 820347; Society of Automotive Engineers, Warrendale, Pa., 1982; "Multi-Fuel Rotary Engine for General Aviation Aircraft" by Jones, Charles; Ellis, David; and Meng, P. R., NASA Technical Memorandum 83429, AIAA-83-1340; National Aeronautics and Space Administration, Washington, D.C., June, 1983. Such prior art suggests the use of lower compression ratios than required for compression ignition engines and it is inferred that engine weight savings would be offered along with a wider range of operation with respect to piston speed and torque requirements. Common problems that such systems present include:
1. Fuel must be mixed with air and delivered in spark ignitable proportions in the spark gap of a spark source at the exact time needed to initiate combustion. This is difficult because of varying degrees of fuel deflection as a result of widely varying velocities of air entry and swirl in the combustion chamber as piston speeds range from idle to full power.
2. Fuel directed towards the spark source from the fuel injector for purposes of producing a suitable mixture of fuel and air for spark ignition invariably reach metallic heat-robbing areas of the combustion chamber around the spark source. This results in combustion process quenching and heat losses through components of the combustion chamber.
3. Spark sources such as spark plugs are prone to fail because of oxidation and excessive heating due to the location they are placed as a result of efforts to place the spark gap as far into the combustion chamber as possible.
4. Spark sources are also prone to become soot coated during portions of the duty cycle and subsequently fail to deliver adequate plasma energy for assured ignition.
5. Widely varying emissions such as soot at some speeds and excessive oxides of nitrogen at other speeds characterize operation at essential portions of the stop-and-go, city-driving duty cycle such as low-speed acceleration, transient conditions and full power.
6. Efforts to overcome the problems arising from undesirable fuel-air ratios at the spark source during important portions of the duty cycle have resulted in efficiency sacrificing practices of air throttling.
(See "Exhaust Emission Control By the Ford Programmed Combustion Process: PROCO", by Simko, A.; Choma, M. A.; and Repko, L. L.; SAE Paper No. 720052, Society of Automotive Engineers, New York, N.Y..)
Another aspect of the problem with such prior art efforts has been the characteristic of requiring highly tuned systems that are adapted to specific fuel properties in order to provide vehicle driveability and to achieve emissions of incomplete combustion and oxides of nitrogen that are acceptable to catalytic clean-up processes in the exhaust stream.
Steam reforming and partial oxidation of hydrocarbons are well-known methods for producing hydrogen. Catalytic steam reforming of light hydrocarbons including natural gas, coal-tar liquids, and petroleum liquids is the least expensive method presently available for producing hydrogen. The use of hydrogen as fuel in heat-engines offers attractive characteristics, particularly including high thermal efficiencies and almost no pollutive emissions.
Efforts to provide technology for reducing the problem of incomplete combustion and to improve thermal efficiency with clean burning hydrogen include the following publications. U.S. Pat. Nos. 4,253,428; 4,362,137; 4,181,100; 4,503,813; 4,515,135; 4,441,469; "Partial Hydrogen Injection Into Internal Combustion Engines Effect On Emissions and Fuel Economy; by Breshears, R.; Cotrill, H.; and Rupe, J.; Jet Propulsion Laboratories and California Institute of Technology, Pasadena, Ca., 1974; "Dissociated Methanol As A Consumable Hydride for Automobiles and Gas Turbines", by Finegold, Joseph G., McKinnon, J. Thomas, and Karpuk, Michael E., Jun. 17, 1982, Hydrogen Energy Progress IV, pp. 1359-1369; "Hydrogen Production From Water By Means of Chemical Cycles", by Glandt, Eduardo D., and Myers, Allan L., Department of Chemical and Biochemical Engineering, University of Pennsylvania, Philadelphia, Pa. 19174; Industrial Engineering Chemical Process Development, Vol. 15, No. 1, 1976; "Hydrogen As A Future Fuel, by Gregory, D. P., Institute of Gas Technology; "On-Board Hydrogen Generator For A Partial Hydrogen Injection I.C. Engine" by Houseman, John, and Cerini, D. J., SAE Paper No. 740600, Society of Automotive Engineers, New York, N.Y.; "On-Board Steam Reforming of Methanol To Fuel The Automotive Hydrogen Engine", by Kester, F. L., Konopta, A. J., and Camara, E. H., I.E.C.E.C. Record-1975, pp. 1176-1183; "Parallel Induction: A Simple Fuel Control Method For Hydrogen Engines", by Lynch, F. E., Hydrogen Energy Progress IV, Jun. 17, 1982, pp. 1033-1051; "Electronic Fuel Injection Techniques For Hydrogen-Powered I.C. Engines", by MacCarley, C. A., and Van Vorst, W. D., International Journal of Hydrogen Energy, Vol. 5, No. 2, Mar. 31, 1980, pp. 179-205.
Definite advantages have been demonstrated by adding hydrogen to hydrocarbon fuels in spark-ignited and in compression-ignited engines. Combustion is more complete and radiation losses are reduced by decreasing the carbon to hydrogen mass ratio. Difficult and notorious problems include low fuel-storage density, back-firing in the intake system, reduced air-breathing capacity as hydrogen contains much less energy per volume measure than gasoline and other hydrocarbon vapors, reduced engine-power ratings, and an increased danger of fire in underhood and hydrogen storage areas.
In addition to powering transportation vehicles, internal combustion engines power many stationery devices. Rising electric rates and urgent needs to improve the air quality in heavily populated areas provide an important opportunity for internal combustion engine powered electric generators and air conditioning systems. Total energy, cogeneration, and hot-tap engine drive systems generally connotate on-site use of the heat rejected by an engine along with the shaft energy to reduce the overall energy consumption and pollutive load on the environment by 40 to 75%. Such systems usually consist of an internal combustion engine, waste heat recovery exchangers to safely interface potable water with cooling jacket water and exhaust gases, and a driven load such as an electric generator or a heat pump compressor. Problems with such systems include low thermal efficiency of the internal combustion engine, inadequate heat recovery from the heat exchangers and inadequate life of engines. Corollaries of the last mentioned problem are unacceptable maintenance requirements and high repair expenses.